Results of electrophysiological investigations of aging in the rodent hippocampus contradict the popular conception of the aging process as one of general deterioration. Such studies have revealed a selective pattern of both degenerative change and functional sparing in different physiological parameters of the same cells. In synaptic transmission, changes have been observed that might even be considered compensatory. The selectivity of the aging process is further demonstrated by the fact that it exhibits clear regional specificity, even among the different subfields of the hippocampus. The future challenges will be to understand both how these specific patterns of age-related neurobiological change arise, and how they lead to the cognitive changes that arise during normal aging.